Since various raw materials such as crude oil are typically mixtures of many compounds in many cases, such various raw materials are often used after being separated into compounds, instead of directly industrially used. A representative process from among chemical processes for separating a mixture is a distillation process. In general, since a distillation process separates a raw material into a high boiling component and a low boiling component, when the number of components of a mixture to be separated is n, the number of distillation columns is n−1 which is obtained by subtracting 1 from the number (n). That is, a process for separating a high-purity product from a crude raw material in the conventional distillation industry mostly uses a structure in which 2 distillation columns are continuously arranged.
As shown in FIG. 1, a conventional distillation process uses a 2-column method of separating a low boiling component D in a first column 11, and separating a medium boiling component S and a high boiling component B in a second column 21.
A composition profile in a first column in a conventional 2 column distillation method which is a typical process of distilling alcohols is shown in FIG. 2. As shown in FIG. 2, the medium boiling component B is generally re-mixed in a lower part of the first column. In particular, when neopentyl glycol is separated as a medium boiling component, a composition profile in the first column is shown in FIG. 3. As shown in FIG. 3, even when neopentyl glycol is used, the medium boiling component is re-mixed in a lower part of the first column.
Although the conventional distillation process may easily control a composition of a product, the conventional distillation process has problems in that a medium boiling component is re-mixed and diluted in a first distillation column. This remixing effect leads to additionally unnecessary energy consumptions because of a thermal inefficiency.
In order to solve these problems, many studies have been done on a new distillation structure. A representative attempt to improve separation efficiency through a thermally coupled structure is a Petlyuk distillation column structure as shown in FIG. 4. A Petlyuk distillation column includes a pre-fractionator 12 and a main column 22 which are thermally coupled to each other such that a low boiling component and a high boiling component are first separated in the pre-fractionator 12, then a top portion and a bottom portion of the pre-fractionator 12 are respectively loaded into inflow plates of the main column 22, and a low boiling component D, a medium boiling component S, and a high boiling component B are separated from one another in the main column 22. In the Petlyuk distillation column structure, since a distillation curve in the Petlyuk distillation column is similar to an equilibrium distillation curve, energy efficiency is high. However, it is not easy to design a process and operate the Petlyuk distillation column, and it is particularly difficult to balance a pressure in the Petlyuk distillation column.